With the rise of the third generation semiconductor materials starting with the breakthrough of p-type doped GaN (gallium nitride) material, accompanied by the technology breakthrough of the high-luminance LED (Light Emitting Diode, LED) based on group III nitride, the nitride based LED for a new generation of solid state lighting source that is green and environmental protective is becoming a new research hotspot. Group III nitride semiconductors, mainly based on GaN (gallium nitride), InGaN (indium gallium nitride), and AlGaN (aluminum gallium nitride) that are ideal materials for manufacturing high-luminance light emitting device, are provided with many excellent features such as wide direct band gap, high internal and external quantum efficiency, high thermal conductivity, good temperature resistance, good corrosion resistance, good shock resistance, and high strength and hardness, etc.
Currently, with the continuous upgrade on the LED application and the market demand of the LED, the LED technology is evolving towards to high power and high luminance. However, as the rapid development of high-power LED lighting industry, often several or dozens, even hundreds of LEDs are connected in series or in parallel in order to prepare a high-voltage LED device. The structure of this kind of high-voltage LED device is provided with too many bonding wires, too much cost and too large area, also a crowding effect of the current density is prone to take place regionally because of auger recombination under a large circuit condition, causing the photosynthetic efficiency of LED declines linearly. While under the same output power, the high-voltage LED device need less driving current than the low-voltage LED does, but exhibits higher photosynthetic efficiency. In view of this, it is necessary to find other new design, new process and new project for the high-voltage LED preparation.